1. Field of the Invention
This invention relates, in general, to hydraulic couplings, and specifically to hydraulic couplings used in undersea drilling and production applications. More particularly, the invention involves an undersea hydraulic coupling having a pair of pressure energized metal seals for sealing between the male member and the female member of the coupling.
2. Description of the Related Art
Subsea hydraulic couplings are old in the art. The couplings generally consist of a male member and a female member with seals to seal the junction between the male and female members.
The female member generally has a cylindrical body with a relatively large diameter bore at one end and a relatively small diameter bore at the other. The small bore facilitates connections to hydraulic lines, while the large bore contains the seals and receives the male portion of the coupling. The male member includes a cylindrical portion at one and to facilitate connection to hydraulic lines. When the cylindrical portion of the male member is inserted into the large bore of the female member, according to various embodiments of the device, the seals either abut the end, or face, of the male member or engage the male member about its circumference. The hydraulic fluid is then free to flow through the female and male portions of the coupling, and seals prevent that flow from escaping about the joints in the coupling.
A check valve may be installed in the female member and also in the male member. Each check valve is open when the coupling is made up; however, each check valve closes when the coupling is broken so as to prevent fluid from leaking out of the system of which the coupling is a part.
Soft seals used in undersea hydraulic couplings have numerous disadvantages, the principal ones being: 1) the inability of the seal to withstand the deteriorating effects of the subsea environment for extended periods of time; and 2) the inability of the soft seal to contain the higher pressures being imposed on hydraulic systems.
A metal seal is available which better withstands both deteriorating effects of the environment and higher pressures. That seal is a crush type seal which is positioned between the end of the male portion of the coupling and the internal end of the large bore in the female portion. When the male portion is inserted into the female, the metal seal is crushed between the two portions and the seal is effectuated between the two. In view of the crushing action, the seal can be used only once. If the coupling is separated for any reason, the once crushed seal can be replaced with a new seal. An example of this type of coupling and seal is shown in U.S. Pat. No. 3,918,485.
Another type of hydraulic coupler with a metal seal is disclosed in U.S. Pat. No. 4,637,470. As may be seen, this design uses a v-shaped metal seal. The metal v-shaped seal rests in the female member and is only effective when it is tightly compressed by pressure from the leading face of the male member. This means that substantial forces are needed to lock the coupling in the first place and to keep it locked under the necessary pressure. This design could leak even upon slight separation of the male and female coupling members, which is a problem because of the internal pressures when each hydraulic line is pressured up, as discussed above. The v-seal coupling requires a pre-load mechanism to prevent separation of the coupling members. Extremely close tolerances are required both for the couplings and manifold plates. In principal, the v-seal coupling was reusable and the coupling could be disengaged and reengaged more than once without replacing the seal. In practice, however, the v-seal would quite often flip out or flip sideways when the coupling was disconnected. If the coupling was reconnected without repositioning the v-seal, the coupler would be damaged beyond use.
In U.S. Pat. No. 4,694,859 to Robert E. Smith III, an undersea hydraulic coupling with a radial metal seal is disclosed. This coupling provides a reusable radial metal seal which engages the circumference of the probe when it is positioned within the female member body. The metal seal is held in place by a cylindrical body or retainer. The retainer prevents escape of the metal seal from the female member body. When the male and female portions of the coupling are parted under pressure, the retainer prevents the metal seal from blowing out through the bore of the female member. This coupling uses a pressure actuated metal c-ring seal. Among the advantages of this design are that it requires no pre-load mechanism, is tolerant to movement of the two halves of the coupling relative to one another, and allows greater tolerances between the couplings and the manifold plates. The retainer also may be used to pre-load the metal c-ring seal by urging it radially inwardly to engage the circumference of the male member. This is accomplished by positioning the seal on a shoulder within the female member bore, then locking the retainer against the seal.
In U.S. Pat. Nos. 4,832,080, 5,099,882 and 5,277,225 to Robert E. Smith III, undersea hydraulic couplings are shown having at least two radial metal seals for sealing between the male member and the female member receiving chamber. Pressure energized seals are shown which are configured to seal radially between the male and female members, and the couplings are pressure balanced for fluid communication through mating radial passages and the annular space between the members.
In U.S. Pat. No. 5,015,016 to Robert E. Smith III, an undersea hydraulic coupling is shown having a ring-shaped metal seal with a v-shaped cross section. A cylindrical sleeve retains the seal in place. Upon insertion of the male member into the coupling, the end face of the male member contacts the lip of the v-seal, which compresses the v-seal slightly to pre-load the seal before pressurization of the coupling. When the system is pressure energized, the sleeve is urged toward the male member to keep the v-seal against the male member. The pressurization urges the v-seal to expand longitudinally against the leading face of the male member and the internal shoulder of the sleeve member.